Referring to FIGS. 10 and 11, the conventional shelf (40) comprises at least four vertical poles (41), and a plurality of shelf boards (42) are respectively assembled therebetween. Each of the poles (41) has a plurality of locating washers coupled on an outer surface thereof, and each of four corners of the single shelf board (42) comprises a collar (421) which is configured to couple with the locating washer to secure the shelf board between the four vertical poles (41).
However, the conventional shelf is disadvantageous because: when two or more shelfs (40) need to be used in parallel, although the shelfs (40) can be bound together through straps, the structure of shelfs is not firm enough and easy to collapse. Another way to connect two shelfs (40) for use is to use additional shelf boards (42a) connected therebetween. Nevertheless, the method is also not desirable because the shelfs (40) have to be disassembled before assembling the additional shelf boards (42a) therebetween, which wastes time, and the additional shelf boards (42a) need to cooperate with the collars (421) to assemble on the poles (41), which makes the additional shelf boards (42a) unable to be assembled at a height level same as the shelf boards (42) of the shelf (40), thereby reducing the practicability. Therefore, there remains a need for a new and improved design for a connector for shelf assembly to overcome the problems presented above.